Processes for conjointly producing bromine, calcium chloride, and chlorine

ABSTRACT

Processes are provided for conjointly producing Br 2 , a concentrated aqueous solution containing CaCI 2 , and Cl 2  from an aqueous HBr-rich stream and a feed brine dilute in CaCI 2  that comprises NaCI. Such processes can comprise feeding the aqueous HBr-rich stream and the feed brine to a tower, oxidizing bromide moieties within the tower with Cl 2  from a Cl 2  source, at least a portion of which is produced according to this invention, to produce Br 2 , recovering Br 2  from the tower, removing a bromide-depleted bottoms from the tower, such bottoms containing HCI, adding a Ca ++  source to the bromide-depleted bottoms to convert substantially all of the HCI in the bottoms to CaCI 2 , as necessary, removing water from the treated bottoms to produce the concentrated aqueous solution, producing Cl 2  and caustics from residual chlorides such as NaCI, and using at least a portion of the thus produced Cl 2  in the Cl 2  source.

BACKGROUND

The present invention relates to processes for conjointly producingbromine, a concentrated aqueous solution of calcium chloride, andchlorine. Further this invention relates to such processes wherein atleast a portion of the produced chlorine is used in the production ofbromine.

Bromine is useful in a wide range of industries. For example, bromine isused in the manufacture of brominated flame retardants such astetrabromobisphenol, decabromodiphenylethane, decabromodiphenyloxide,and brominated polystyrenes. Bromine is also used, e.g., in themanufacture of 1,2-dibromoethane, which is used as a petrol additive, inthe manufacture of compounds used in photography (e.g. silver bromide,which is the light sensitive material in film), in the manufacture ofdyestuffs and drugs, in analytical laboratory in testing forunsaturation in organic compounds, as a disinfectant, and in goldextraction. Calcium chloride is also useful in numerous applications,e.g., as a drying agent, in ice and dust control, in oil well drilling,in food processing, in concrete mixtures to speed up setting, as anadditive in plastics, and as a drainage aid for wastewater treatment.

One source used in production of bromine and calcium chloride is brine.Brine is an aqueous solution nearly saturated with halide salts andwhich is produced in several areas of the United States. Such producedbrines typically contain at least sodium chloride, sodium bromide andcalcium chloride. Additionally, certain processes, such as processes forproducing brominated flame retardants, generate substantial quantitiesof hydrogen bromide as a by-product, which can be converted to bromine.

Processes for production of bromine from these and otherbromide-containing solutions are well know. For example, bromine can beproduced by a bromine steaming out process, such as Kubierschky'sdistillation method; see, e.g., Kirk-Othmer, Encyclopedia of ChemicalTechnology, Fourth Edition, volume 4, pages 548 through 553. Othermethods for recovering bromine from bromide-containing solutions aredescribed, e.g., in U.S. Pat. Nos. 3,181,934, 4,719,096, 4,978,518,4,725,425, 5,158,683, and U.S. Pat. No. 5,458,781.

Substantial quantities of chlorine (Cl₂) are used in Kubierschky'sdistillation method, and in other methods for production of bromine.Chlorine is typically produced using an electrolysis method, several ofwhich are known to those skilled in the art. Thus-produced chlorine iswet and caustic; and containers made from costly materials are requiredfor its transport. The chlorine can be dried, compressed and cooled fortransport, which is a costly endeavor. In some cases, chlorine isproduced on site and sent directly to the process for production ofbromine via pipeline. While costs associated with transporting chlorinemake on-site production of chlorine attractive, in any of thesecircumstances, the cost of providing chlorine can add significantly tothe cost of producing bromine.

Processes for production of calcium chloride from brines and othersources are also well known. See, e.g., U.S. Pat. No. 4,704,265, WO03/035550, and U.S. Pat. No. 6,524,546.

Even in view of these and other published methods for production ofbromine and for production of calcium chloride, it would be commerciallybeneficial to have processes for conjointly producing bromine, calciumchloride and chlorine, wherein at least a portion of the producedchlorine can be used in the production of bromine.

THE INVENTION

This invention meets the above-described needs by providing processesfor conjointly producing Br₂, a concentrated aqueous solution comprisingfrom about 5 wt % CaCl₂ to about 40 wt % CaCl₂, based on the weight ofthe concentrated aqueous solution, and Cl₂, which processes comprise:(a) feeding an aqueous HBr-rich stream either together or separatelywith a feed brine dilute in CaCl₂ to a tower, wherein the feed brinecomprises at least about 10 wt % chlorides, based on the total weight ofthe feed brine; (b) oxidizing bromide moieties within the tower with Cl₂to produce Br₂; (c) recovering Br₂ from the tower; (d) removingbromide-depleted bottoms from the tower, such bottoms comprising lessthan about 5 wt % HCI, based on the weight of the bromide-depletedbottoms; (e) adding a Ca⁺⁺ source to the bromide depleted bottoms toconvert substantially all of the HCI in the bottoms to CaCl₂; (f)removing at least a portion of the chlorides and, as necessary removingwater, from the treated bottoms from (e) to produce the concentratedaqueous solution; and (g) producing Cl₂ from at least a portion of theremoved chlorides. Also provided are processes for conjointly producingBr₂, a concentrated aqueous solution comprising from about 5 wt % CaCl₂to about 40 wt % CaCl₂, based on the weight of the concentrated aqueoussolution, and Cl₂, which processes comprise: (a) feeding an aqueousHBr-rich stream either together or separately with a feed brine dilutein CaCl₂ to a tower, wherein the feed brine comprises at least about 10wt % chlorides, based on the total weight of the feed brine; (b)oxidizing bromide moieties within the tower with Cl₂ to produce Br₂,wherein at least a portion of the Cl₂ is from (g); (c) recovering Br₂from the tower; (d) removing bromide-depleted bottoms from the tower,such bottoms comprising less than about 5 wt % HCI, based on the weightof the bromide-depleted bottoms; (e) adding a Ca⁺⁺ source to the bromidedepleted bottoms to convert substantially all of the HCI in the bottomsto CaCl₂; (f) removing at least a portion of the chlorides and, asnecessary removing water, from the treated bottoms from (e) to producethe concentrated aqueous solution; and (g) producing Cl₂ from at least aportion of the removed chlorides. Also provides are any of the processesdescribed herein, wherein the chlorides comprise NaCl, wherein (g)includes producing caustics with the Cl₂, and/or wherein in (f) heat isused in removing water from the treated bottoms in the form of steam andthe steam is recycled for use in a bromine steaming out process.

FIGURES

The invention is better understood by reference to the FIGURE, which isa flow diagram representative of processes according to this invention.

PROCESS DESCRIPTION

Referring to the FIGURE, in one process according to this invention anaqueous HBr-rich stream 10 is fed to tower 20. Optionally, at least aportion of feed brine stream 30, dilute in CaCl₂ is fed to tower 20.Feed brine stream 30 can comprise at least about 10 wt % chlorides up tosaturation, e.g., can comprise about 10 wt % up to about 25 wt % NaClbased on the total weight of feed brine stream 30. Stream 40 comprisingsource of Cl₂ is also fed to tower 20. Streams 10, 40, and optionally30, can be fed together or separately to tower 20. Inside tower 20,bromide moieties are oxidized with Cl₂ to produce Br₂ and HCI. Stream 50comprising produced Br₂ is recovered from tower 20. Stream 70 comprisingCa⁺⁺ source is combined with stream 60 comprising bromide-depletedbottoms to convert substantially all of the HCI in the bottoms to CaCl₂;i.e., stream 72 comprises CaCl₂ and essentially no HCI. As necessary,stream 80 comprising water in the form of steam is removed from the Ca⁺⁺treated bottoms via device 75 to produce stream 90 comprising aconcentrated aqueous solution of at least about 5 wt % CaCl₂, based onthe weight of the concentrated aqueous solution. Device 75 can be anydevice suitable for the process, such as a tank, filter, or centrifuge,to name a few. Additionally, stream 85 comprising chlorides can be fedto device 120 where Cl₂ and caustics are produced from the chlorides viaan electrolysis method, or other method, as will be familiar to thoseskilled in the art. For example, when stream 85 comprises NaCl, Cl₂ andNaOH are produced. At least a portion of produced Cl₂ in stream 130 isfed to tower 20, for example, via stream 40. Device 120 can be anydevice suitable for use in producing Cl₂ and caustics from chlorides,such as NaCl. Such devices will be familiar to those skilled in the art.Stream 85 can comprise other chlorides, for example MgCl, FeCl, KCl,NH₄Cl, and the like, that are also suitable for producing Cl₂;alternatively, stream 85 can consist essentially of NaCl. Processes ofthis invention also encompass production of Cl₂ from other componentsand use of at least a portion of the thus produced Cl₂ in the process ofbromine production, e.g., in tower 20. Additionally, at least a portionof the Cl₂ produced according to this invention can be sold or used forother purposes, such as in other processes that use Cl₂. Producedcaustics, such as NaOH, Mg(OH)₂, Ca(OH)₂, KOH, and the like, can be usedor sold.

In another such process according to this invention, stream 80comprising water in the form of steam is removed from the Ca⁺⁺ treatedbottoms via device 75.

In known processes for producing Br₂, stream 60 comprisingbromide-depleted bottoms can be treated with ammonia or a caustic suchas NaOH, MgOH, or the like, to neutralize substantially all of the HCI.In an improvement to such a process according to this invention, stream70 comprising Ca⁺⁺ source is combined with stream 60 comprisingbromide-depleted bottoms to convert substantially all of the HCI in thebottoms to CaCl₂. Thus stream 72 comprises CaCl₂ and essentially no HCI.This improvement is beneficial in that the cost to treat with a Ca⁺⁺source is typically less than the cost to treat with ammonia or acaustic, and treatment with a Ca⁺⁺ source produces CaCl₂, which can besold commercially.

In one process according to this invention, aqueous HBr-rich stream 10that is fed to tower 20 contains amines. The amines can be by-productsfrom other commercial processes and can be available in streams thatalso contain NaBr. For example, amines can be present in aqueousHBr-rich stream 10 when stream 10 is produced by combining a liquid withan HBr-rich recycle stream resulting from production ofalkyldimethylamine, which is useful, e.g., in production of quaternaryamines, amine oxides, and betaines, which in turn are useful incleaners, disinfectants, wood treatments, personal care products,oilfield products, and water treatment products. A recycle stream fromproduction of alkyldimethylamine can comprise amines and sodium bromide.Bromine in the presence of amine compounds can lead to production ofby-products that are shock sensitive. In this process, however, feedbrine stream 30 comprises at least about 10 wt % NaCl up to about 25 wt% NaCl (typically about 20 wt % to about 25 wt %), based on the totalweight of feed brine stream 30; also, aqueous HBr-rich stream 10 has apH of less than about 4, or less than about 2, or even less than aboutzero. The tendency of bromines in solution with amines to produce shocksensitive by-products is significantly reduced in this process due tothe combination in tower 20 of stream 30 comprising at least about 10 wt% NaCl and stream 10 having a pH of less than about 4. Thus, brominesand amines in tower 20 do not tend to produce shock-sensitiveby-products; and amines can be removed from tower 20 with bromine instream 50. NaCl from stream 30 can be removed via device 75 via stream85 comprising NaCl.

Aqueous HBr-Rich Stream

Aqueous HBr-rich stream 10 that is fed to tower 20 comprises at leastabout 3 wt % HBr, based on the total weight of stream 10, up to the HBrsaturation limit of stream 10, e.g., up to about 60 wt % HBr, based onthe total weight of stream 10. Aqueous HBr-rich stream 10 can alsocomprise varying amounts of other components such as NaBr. AqueousHBr-rich stream 10 can be produced, e.g., by combining gaseous HBr witha liquid comprising brine, fresh water, or another water source. Thegaseous HBr can come from an HBr-rich recycle stream, e.g., any streamcomprising HBr.

Feed Brine Dilute in CaCl₂

Feed brine stream 30 dilute in CaCl₂ comprises at least about 5 wt %CaCl₂ based on the total weight of stream 30. The upper limit of CaCl₂in stream 30 depends upon the feed brine source, and can be based onwhatever amount of CaCl₂ naturally occurs in the brine, which typicallyis no more than about 15 wt % CaCl₂ based on the weight of the brine.Stream 30 can also comprise varying amounts of other components such asNaBr and NaCl.

Source of Cl₂

Stream 40 comprising source of Cl₂ can comprise essentially 100 wt %elemental chlorine, and can also comprise some water, e.g., up to about5 wt % or more. Cl₂ can be purchased from commercial providers or can beproduced from, e.g., a feed brine, through electrolysis, as will befamiliar to those skilled in the art. However, according to thisinvention, at least a portion of stream 40 comprises Cl₂ producedaccording to this invention.

Oxidation of Bromide Moieties with Cl₂

As will be familiar to those skilled in the art, oxidation of bromidemoieties with Cl₂ to produce Br₂ in tower 20 can occur, e.g., due to thereaction: 2HBr+Cl₂→Br₂+2HCI and/or the reaction: 2NaBr+Cl₂→Br₂+2NaCl,among others. Tower 20 can be any suitable tower for oxidizing bromidemoieties with Cl₂ to produce Br₂, as will be familiar to those skilledin the art. In processes according to this invention, the acidic pH ofaqueous HBr-rich stream 10 provides an economic benefit in that the feedbrine in stream 30 typically contains impurities such as NH₃ and H₂S,which react with Cl₂. These reactions are inhibited at low pH, e.g., pHless than about 4, thereby improving Cl₂ utilization.

Bromide-Depleted Bottoms

Stream 60 comprising bromine-depleted bottoms can comprise water, HCI,NaCl, CaCl₂, and other components that result from the oxidation ofbromide moieties with Cl₂ to produce Br₂ and that may pass through tower20 from stream 10, stream 30, or stream 40 unchanged. Typically, stream60 comprises essentially no bromide moieties to very small amounts ofbromide moieties, e.g., from about 50 ppm to about 400 ppm bromidemoieties. Stream 60 comprising bromide-depleted bottoms typicallycomprises less than about 5 wt % HCI based on the total weight of stream60, and can comprise 1 wt % HCI to about 5 wt % HCI. In some commercialapplications, stream 60 can comprise up to about 35 wt % HCI.

Ca⁺⁺ Source

Stream 70 comprising Ca⁺⁺ source can comprise any suitable source ofCa⁺⁺ that is now known or comes to be known, including withoutlimitation lime, Ca(OH)₂, and CaCO₃, as will be familiar to thoseskilled in the art.

Conversion of HCI To CaCl₂

Once stream 70 comprising Ca⁺⁺ source is combined with stream 60comprising bromide-depleted bottoms, CaCl₂ can be generated, e.g., bythe reaction 2HCI+CaCO₃→CaCl₂+H₂O+CO₂, and/or the reaction2HCI+CaO→CaCl₂+H₂O, and/or the reaction 2HCI+Ca(OH)₂→CaCl₂+2H₂O, amongothers. Thus stream 72 comprises essentially no HCI, and comprises moreCaCl₂ and more H₂O than stream 60. Stream 72 can consist essentially ofH₂O, NaCl and CaCl₂.

Removing H2O from Ca⁺⁺ Treated Bottoms

Stream 80 comprising water that is removed from the Ca⁺⁺ treated bottomsvia device 75 comprises primarily water in the form of steam. The watercan be removed by heating of the contents of device 75, generally withsteam, or via any other heating means, as will be familiar to thoseskilled in the art.

Concentrated Aqueous Solution

Stream 90 comprising a concentrated aqueous solution of at least about 5wt % CaCl₂, based on the weight of the concentrated aqueous solution,can comprise CaCl₂ up to the saturation limit of the concentratedaqueous solution. Typically, the concentrated aqueous solution comprisesat least about 5 wt % CaCl₂, and can comprise from about 5 wt % CaCl₂ toabout 40 wt % CaCl₂. The concentrated aqueous solution can be furtherprocessed to produce a substantially 100% composition of CaCl₂, whichwill typically be flaked CaCl₂.

Production of Cl₂

Cl₂ is produced, e.g., from NaCl in stream 85. Processes for producingCl₂ and caustics from chlorides are well known. For example, Cl₂ andNaOH can be produced from NaCl₂ by membrane cell electrolysis or bydiaphragm electrolysis.

EXAMPLE

The following example is illustrative of the principles of thisinvention. It is understood that this invention is not limited to anyone specific embodiment exemplified herein, whether in the examples orthe remainder of this patent application.

Referring to the FIGURE, aqueous HBr-rich stream 10 comprises 5838lbs/hour HBr, 360 lbs/hour NaBr, and 19194 lbs/hour H₂O; i.e., stream 10comprises about 23 wt % HBr, about 1 wt % NaBr, and about 76 wt % H₂O,based on the total weight of stream 10. In this example, aqueous HBr-rich stream 10 is comprised of streams from various processes, someof which make brominated flame retardants and some of which compriseamines. Feed brine stream 30 comprises 320 lbs/hour NaBr, 58134 lbs/hourH₂O, 22834 lbs/hour NaCl, and 10047 lbs/hour CaCl₂; i.e., stream 30comprises about 0.4 wt % NaBr, about 63.6 wt % H₂O, about 25 wt % NaCl,and about 11 wt % CaCl₂, based on the total weight of stream 30. Stream40 comprises at least about 2593 lbs/hour elemental chlorine, which isproduced according to this invention, and only trace amounts of water.Streams 10, 30, and 40 are combined and input to tower 20. Inside tower20, bromide moieties from streams 10 and 30 are oxidized with Cl₂ fromstream 40 to produce Br₂ in a standard steaming out process, and stream50 comprising about 5844 lbs/hour Br₂ is recovered from tower 20. Stream60 is recovered from tower 20 by means known to those skilled in theart, and comprises 77277 lbs/hour H₂O, 2392 lbs/hour HCI, 22834 lbs/hourNaCl, and 10047 lbs/hour CaCl₂; i.e., stream 60 comprises about 68.7 wt% H₂O, about 2.1 wt % HCI, about 20.3 wt % NaCl, and about 8.9 wt %CaCl₂, based on the total weight of stream 60. Stream 70 comprises 3323lbs/hour CaCO₃; i.e., stream 70 comprises 100 wt % CaCO₃. Stream 72results from combination of streams 60 and 70 and the conversion of HCIfrom stream 60 by CaCO₃ from stream 70 to CaCl₂ and H₂O; and stream 72comprises 78524 lbs/hour H₂O, 22834 lbs/hour NaCl, and 13702 lbs/hourCaCl₂; i.e., stream 72 comprises about 68.2 wt % H₂O, about 19.9 wt %NaCl, and about 11.9 wt % CaCl₂, based on the total weight of stream 72.Stream 72 is input to tank 75, which is heated by steam (heating meansnot illustrated). NaCl in stream 72 (carried forward from stream 30) isremoved from tank 75 via stream 85 comprising 22834 lbs/hour NaCl.Stream 80 comprising 57972 lbs/hour H₂O, i.e., essentially 100 wt % H₂Obased on the weight of stream 80, which H₂O is in the form of steam dueto the heating of tank 75 with steam, is used to heat tower 20 or tank75. Calcium chloride (comprising produced CaCl₂ and CaCl₂ carriedforward from stream 30) are recovered from tank 75 via stream 90 whichcomprises 20552 lbs/hour H₂O and 13702 lbs/hour CaCl₂, i.e., about 60 wt% H₂O and about 40 wt % CaCl₂, based on the total weight of stream 90.Economic benefit is derived from the sale of stream 90 as is or by saleof flaked CaCl₂ from stream 90, produced by means familiar to thoseskilled in the art. In addition, stream 85 comprising 22834 lbs/hourNaCl is fed to membrane cell electrolysis device 120. Stream 130comprising 2593 lbs/hour Cl₂ is recovered from membrane cellelectrolysis device 120 and fed into stream 40. 6346 lbs/hour NaOH and11264 lbs/hour Cl₂ are otherwise recovered from membrane cellelectrolysis device 120 (recovery not illustrated in the FIGURE).

It is to be understood that the reactants and components referred to bychemical name or formula anywhere in the specification or claims hereof,whether referred to in the singular or plural, are identified as theyexist prior to being combined with or coming into contact with anothersubstance referred to by chemical name or chemical type (e.g., anotherreactant, a solvent, or etc.). It matters not what chemical changes,transformations and/or reactions, if any, take place in the resultingmixture or solution or reaction medium as such changes, transformationsand/or reactions are the natural result of bringing the specifiedreactants and/or components together under the conditions called forpursuant to this disclosure. Thus the reactants and components areidentified as ingredients to be brought together in connection withperforming a desired chemical reaction or in forming a mixture to beused in conducting a desired reaction. Accordingly, even though theclaims hereinafter may refer to substances, components and/oringredients in the present tense (“comprises”, “is”, etc.), thereference is to the substance, component or ingredient as it existed atthe time just before it was first contacted, combined, blended or mixedwith one or more other substances, components and/or ingredients inaccordance with the present disclosure. Whatever transformations, ifany, which occur in situ as a reaction is conducted is what the claim isintended to cover. Thus the fact that a substance, component oringredient may have lost its original identity through a chemicalreaction or transformation during the course of contacting, combining,blending or mixing operations, if conducted in accordance with thisdisclosure and with the application of common sense and the ordinaryskill of a chemist, is thus wholly immaterial for an accurateunderstanding and appreciation of the true meaning and substance of thisdisclosure and the claims thereof.

While the present invention has been described in terms of one or morepreferred embodiments, it is to be understood that other modificationsmay be made without departing from the scope of the invention, which isset forth in the claims below.

What is claimed is:
 1. A process comprising: (a) feeding an aqueousHBr-rich stream either together or separately with a feed brine dilutein CaCl₂ to a tower, wherein the feed brine comprises at least about 10wt % NaCl, based on the total weight of the feed brine, and wherein theHBr-rich stream comprises amine by-products from one or more commercialprocesses and has a pH of less than about 4, such that production ofshock-sensitive-by-products in the tower is minimized; (b) oxidizingbromide moieties within the tower with Cl₂ to produce Br₂; (c)recovering Br₂ from the tower; (d) removing bromide-depleted bottomsfrom the tower, such bottoms comprising less than about 5 wt % HCl,based on the weight of the bromide-depleted bottoms; (e) adding a Ca⁺⁺source to the bromide depleted bottoms to convert substantially all ofthe HCl in the bottoms to CaCl₂; (f) removing at least a portion of theNaCl and, as necessary, removing water, from the treated bottoms from(e) to produce a concentrated aqueous solution comprising from about 5wt % CaCl₂ to about 40 wt % CaCl₂; (g) recovering the concentratedaqueous solution comprising from about 5 wt % CaCl₂ to about 40 wt %CaCl₂; (h) producing Cl₂ from at least a portion of the removed NaCl. 2.The process according to claim 1, wherein (h) includes producingcaustics with the Cl₂.
 3. The process according to claim 1, wherein in(f) heat is used in removing water from the treated bottoms in the formof steam and the steam is recycled for use in a bromine steaming outprocess.
 4. A process comprising: (a) feeding an aqueous HBr-rich streameither together or separately with a feed brine dilute in CaCl₂ to atower, wherein the feed brine comprises at least about 10 wt % NaCl,based on the total weight of the feed brine, and wherein the HBr-richstream comprises amine by-products from one or more commercial processesand has a pH of less than about 4, such that production ofshock-sensitive-by-products in the tower is minimized; (b) oxidizingbromide moieties within the tower with Cl₂ to produce Br₂, wherein atleast a portion of the Cl₂ is from (h); (c) recovering Br₂ from thetower; (d) removing bromide-depleted bottoms from the tower, suchbottoms comprising less than about 5 wt % HCl, based on the weight ofthe bromide-depleted bottoms; (e) adding a Ca⁺⁺ source to the bromidedepleted bottoms to convert substantially all of the HCl in the bottomsto CaCl₂; (f) removing at least a portion of the NaCl and, as necessary,removing water, from the treated bottoms from (e) to produce aconcentrated aqueous solution comprising from about 5 wt % CaCl₂ toabout 40 wt % CaCl₂; (g) recovering the concentrated aqueous solutioncomprising from about 5 wt % CaCl₂ to about 40 wt % CaCl₂; (h) producingCl₂ from at least a portion of the removed NaCl.